We aim to understand the effects of hydration changes on athletes’ neuromuscular performance, on body water compartments, fat-free mass hydration and hydration biomarkers and to test the effects of the intervention on the response of acute dehydration in the hydration indexes. The H2OAthletes study (clinicaltrials.gov ID: NCT05380089) is a randomised controlled trial in thirty-eight national/international athletes of both sexes with low total water intake (WI) (i.e. < 35·0 ml/kg/d). In the intervention, participants will be randomly assigned to the control (CG, n 19) or experimental group (EG, n 19). During the 4-day intervention, WI will be maintained in the CG and increased in the EG (i.e. > 45·0 ml/kg/d). Exercise-induced dehydration protocols with thermal stress will be performed before and after the intervention. Neuromuscular performance (knee extension/flexion with electromyography and handgrip), hydration indexes (serum, urine and saliva osmolality), body water compartments and water flux (dilution techniques, body composition (four-compartment model) and biochemical parameters (vasopressin and Na) will be evaluated. This trial will provide novel evidence about the effects of hydration changes on neuromuscular function and hydration status in athletes with low WI, providing useful information for athletes and sports-related professionals aiming to improve athletic performance.

We sought to examine the effects of daily consumption of macadamia nuts on body weight and composition, plasma lipids and glycaemic parameters in a free-living environment in overweight and obese adults at elevated cardiometabolic risk. Utilising a randomised cross-over design, thirty-five adults with abdominal obesity consumed their usual diet plus macadamia nuts (~15 % of daily calories) for 8 weeks (intervention) and their usual diet without nuts for 8 weeks (control), with a 2-week washout. Body composition was determined by bioelectrical impedance; dietary intake was assessed with 24-h dietary recalls. Consumption of macadamia nuts led to increased total fat and MUFA intake while SFA intake was unaltered. With mixed model regression analysis, no significant changes in mean weight, BMI, waist circumference, percent body fat or glycaemic parameters, and non-significant reductions in plasma total cholesterol of 2⋅1 % (−4⋅3 mg/dl; 95 % CI −14⋅8, 6⋅1) and low-density lipoprotein (LDL-C) of 4 % (−4⋅7 mg/dl; 95 % CI −14⋅3, 4⋅8) were observed. Cholesterol-lowering effects were modified by adiposity: greater lipid lowering occurred in those with overweight v. obesity, and in those with less than the median percent body fat. Daily consumption of macadamia nuts does not lead to gains in weight or body fat under free-living conditions in overweight or obese adults; non-significant cholesterol lowering occurred without altering saturated fat intake of similar magnitude to cholesterol lowering seen with other nuts.

Clinical Trial Registry Number and Website: NCT03801837 https://clinicaltrials.gov/ct2/show/NCT03801837?term = macadamia + nut&draw = 2&rank = 1

This study aimed to assess the validity of mid-arm circumference (MAC), also known as mid-upper arm circumference (MUAC), for classification of high body fatness in Namibian adolescent girls and women and to test whether classification accuracy of MUAC was higher than the traditional simple proxy for high fatness, the BMI. In 206 adolescent girls aged 13–19 years and 207 adult women aged 20–40 years, we defined obesity conventionally (BMI-for-age Z score ≥ 2·00, adolescents; adults BMI ≥ 30·0 kg/m2) and also defined obesity using published MAC cut-off values. 2H oxide dilution was used to measure total body water (TBW) to define high body fat percentage (≥ 30 % in the adolescents, ≥ 38 % in the adults), and we compared the ability of BMI and MAC to classify high body fatness correctly using sensitivity, specificity and predictive values. In the adolescents, obesity prevalence was 9·2 % (19/206) using BMI-for-age and 63·2 % (131/206) using TBW; sensitivity of BMI-for-age was 14·5 % (95 % CI 9·1, 22·0 %) but was improved significantly using MAC of 22·6 cm (sensitivity 96·9 %; 95 % CI 92·1 %, 99·3 %). In the adults, obesity prevalence was 30·4 % (63/207) using BMI and 57·0 % (118/207) using TBW, and sensitivity of BMI was 52·5 % (95 % CI 43·6, 62·2 %), but using a MAC of 30·6 cm sensitivity was 72·8 % (95 % CI 66·4, 82·6 %). Surveillance of obesity in African adolescent girls and adult women is likely to be improved substantially by use of MAC as an alternative to the BMI-for-age and BMI.

Few investigations have evaluated the validity of current body composition technology among racially and ethnically diverse populations. This study assessed the validity of common body composition methods in a multi-ethnic sample stratified by race and ethnicity. One hundred and ten individuals (55 % female, age: 26·5 (sd 6·9) years) identifying as Asian, African American/Black, Caucasian/White, Hispanic, Multi-racial and Native American were enrolled. Seven body composition models (dual-energy X-ray absorptiometry (DXA), air displacement plethysmography (ADP), two bioelectrical impedance devices (BIS, IB) and three multi-compartment models) were evaluated against a four-compartment criterion model by assessing total error (TE) and standard error of the estimate. For the total sample, measures of % fat and fat-free mass (FFM) from multi-compartment models were all excellent to ideal (% fat: TE = 0·94–2·37 %; FFM: TE = 0·72–1·78 kg) compared with the criterion. % fat measures were very good to excellent for DXA, ADP and IB (TE = 2·52–2·89 %) and fairly good for BIS (TE = 4·12 %). For FFM, single device estimates were good (BIS; TE = 3·12 kg) to ideal (DXA, ADP, IB; TE = 1·21–2·15 kg). Results did not vary meaningfully between each race and ethnicity, except BIS was not valid for African American/Black, Caucasian/White and Multi-racial participants for % fat (TE = 4·3–4·9 %). The multi-compartment models evaluated can be utilised in a multi-ethnic sample and in each individual race and ethnicity to obtain highly valid results for % fat and FFM. Estimates from DXA, ADP and IB were also valid. The BIS may demonstrate greater TE for all racial and ethnic cohorts and results should be interpreted cautiously.

Understanding the effects of acute feeding on body composition and metabolic measures is essential to the translational component and practical application of measurement and clinical use. To investigate the influence of acute feeding on the validity of dual-energy X-ray absorptiometry (DXA), a four-compartment model (4C) and indirect calorimetry metabolic outcomes, thirty-nine healthy young adults (n 19 females; age: 21·8 (sd 3·1) years, weight; 71·5 (sd 10·0) kg) participated in a randomised cross-over study. Subjects were provided one of four randomised meals on separate occasions (high carbohydrate, high protein, ad libitum or fasted baseline) prior to body composition and metabolic assessments. Regardless of macronutrient content, acute feeding increased DXA percent body fat (%fat) for the total sample and females (average constant error (CE):–0·30 %; total error (TE): 2·34 %), although not significant (P = 0·062); the error in males was minimal (CE: 0·11 %; TE: 0·86 %). DXA fat mass (CE: 0·26 kg; TE: 0·75 kg) and lean mass (LM) (CE: 0·83 kg; TE: 1·23 kg) were not altered beyond measurement error for the total sample. 4C %fat was significantly impacted from all acute feedings (avg CE: 0·46 %; TE: 3·7 %). 4C fat mass (CE: 0·71 kg; TE: 3·38 kg) and fat-free mass (CE: 0·55 kg; TE: 3·05 kg) exceeded measurement error for the total sample. RMR was increased for each feeding condition (TE: 1666·9 kJ/d; 398 kcal/d). Standard pre-testing fasting guidelines may be important when evaluating DXA and 4C %fat, whereas additional DXA variables (fat mass and LM) may not be significantly impacted by an acute meal. Measuring body composition via DXA under less stringent pre-testing guidelines may be valid and increase feasibility of testing in clinical settings.

The present study reports the validity of multiple assessment methods for tracking changes in body composition over time and quantifies the influence of unstandardised pre-assessment procedures. Resistance-trained males underwent 6 weeks of structured resistance training alongside a hyperenergetic diet, with four total body composition evaluations. Pre-intervention, body composition was estimated in standardised (i.e. overnight fasted and rested) and unstandardised (i.e. no control over pre-assessment activities) conditions within a single day. The same assessments were repeated post-intervention, and body composition changes were estimated from all possible combinations of pre-intervention and post-intervention data. Assessment methods included dual-energy X-ray absorptiometry (DXA), air displacement plethysmography, three-dimensional optical imaging, single- and multi-frequency bioelectrical impedance analysis, bioimpedance spectroscopy and multi-component models. Data were analysed using equivalence testing, Bland–Altman analysis, Friedman tests and validity metrics. Most methods demonstrated meaningful errors when unstandardised conditions were present pre- and/or post-intervention, resulting in blunted or exaggerated changes relative to true body composition changes. However, some methods – particularly DXA and select digital anthropometry techniques – were more robust to a lack of standardisation. In standardised conditions, methods exhibiting the highest overall agreement with the four-component model were other multi-component models, select bioimpedance technologies, DXA and select digital anthropometry techniques. Although specific methods varied, the present study broadly demonstrates the importance of controlling and documenting standardisation procedures prior to body composition assessments across distinct assessment technologies, particularly for longitudinal investigations. Additionally, there are meaningful differences in the ability of common methods to track longitudinal body composition changes.

Assessing children’s growth adequately is important due to the necessary prevention of adequate body composition, especially at pre-pubertal age. Simpler measurements such as anthropometry or bioimpedance, using equations validated in Caucasian children, have been demonstrated to overestimate or underestimate fat mass percentage (FM%) or fat-free mass (FFM) in Chilean children. In a sample of 424 children (198 boys and 226 girls) of 7–9 years old, the three component (3C) model was assessed, where total body water was determined by 2H dilution and body volume by air displacement plethysmography, in order to design and validate anthropometry and bioimpedance equations. The FM (%) equation specific for Chilean children was validated as (1·743 × BMI z-score) + (0·727 × triceps skinfold) + (0·385 × biceps skinfold) + 15·985, against the 3C model (R2 0·79). The new FFM equation (kg) generated was (log FFM = (0·018 × age) + (0·047 × sex) + (0·006 × weight) + (0·027 × resistance) + 2·071), with an R2 0·93 (female = 1 and male = 2). The Bland–Altman analysis shows a mean difference of 0·27 (sd 3·5) for the FM% in the whole group as well as 0·004 (sd 0·9) kg is the mean difference for the bioelectrical impedance analysis (BIA) FFM (kg) equation. The new equations for FM (%) and FFM (kg) in Chilean children will provide a simple and valid tool for the assessment of body composition in cohort studies or to assess the impact of nutritional programmes or public policies.

This study reports the validity of body fat percentage (BF%) estimates from several commonly employed techniques as compared with a five-component (5C) model criterion. Healthy adults (n 170) were assessed by dual-energy X-ray absorptiometry (DXA), air displacement plethysmography (ADP), multiple bioimpedance techniques and optical scanning. Output was also used to produce a criterion 5C model, multiple variants of three- and four-component models (3C; 4C) and anthropometry-based BF% estimates. Linear regression, Bland–Altman analysis and equivalence testing were performed alongside evaluation of the constant error (CE), total error (TE), se of the estimate (SEE) and coefficient of determination (R2). The major findings were (1) differences between 5C, 4C and 3C models utilising the same body volume (BV) and total body water (TBW) estimates are negligible (CE ≤ 0·2 %; SEE < 0·5 %; TE ≤ 0·5 %; R2 1·00; 95 % limits of agreement (LOA) ≤ 0·9 %); (2) moderate errors from alternate TBW or BV estimates in multi-component models were observed (CE ≤ 1·3 %; SEE ≤ 2·1 %; TE ≤ 2·2 %; R2 ≥ 0·95; 95 % LOA ≤ 4·2 %); (3) small differences between alternate DXA (i.e. tissue v. region) and ADP (i.e. Siri v. Brozek equations) estimates were observed, and both techniques generally performed well (CE < 3·0 %; SEE ≤ 2·3 %; TE ≤ 3·6 %; R2 ≥ 0·88; 95 % LOA ≤ 4·8 %); (4) bioimpedance technologies performed well but exhibited larger individual-level errors (CE < 1·0 %; SEE ≤ 3·1 %; TE ≤ 3·3 %; R2 ≥ 0·94; 95 % LOA ≤ 6·2 %) and (5) anthropometric equations generally performed poorly (CE 0·6– 5·7 %; SEE ≤ 5·1 %; TE ≤ 7·4 %; R2 ≥ 0·67; 95 % LOA ≤ 10·6 %). Collectively, the data presented in this manuscript can aid researchers and clinicians in selecting an appropriate body composition assessment method and understanding the associated errors when compared with a reference multi-component model.

The purpose of the present study was: (1) to develop a new dual-energy X-ray absorptiometry (DXA)-derived body volume (BV) equation with the GE-Lunar prodigy while utilising underwater weighing (UWW) as a criterion and (2) to cross-validate the novel DXA-derived BV equation (4C-DXANickerson), Wilson DXA-derived BV equation (4C-DXAWilson) and air displacement plethysmography (ADP)-derived BV (4C-ADP) in Hispanic adults. A total of 191 Hispanic adults (18–45 years) participated in the present study. The development sample consisted of 120 females and males (50 % females), whereas the cross-validation sample comprised of forty-one females and thirty males (n 71). Criterion body fat percentage (BF %) and fat-free mass (FFM) were determined using a four-compartment (4C) model with UWW as a criterion for BV (4C-UWW). 4C-DXANickerson, 4C-DXAWilson and 4C-ADP were compared against 4C-UWW in the cross-validation sample. 4C-DXANickerson, 4C-DXAWilson and 4C-ADP all produced similar validity statistics when compared with 4C-UWW in Hispanic males (all P > 0·05). 4C-DXANickerson also yielded similar BF % and FFM values as 4C-UWW when evaluating the mean differences (constant error (CE)) in Hispanic females (CE = –0·79 % and 0·38 kg; P = 0·060 and 0·174, respectively). However, 4C-DXAWilson produced significantly different BF % and FFM values (CE = 3·22 % and –2·20 kg, respectively; both P < 0·001). Additionally, 4C-DXAWilson yielded significant proportional bias when estimating BF % (P < 0·001), whereas 4C-ADP produced significant proportional bias for BF % and FFM (both P < 0·05) when evaluated in Hispanic females. The present study findings demonstrate that 4C-DXANickerson is a valid measure of BV in Hispanics and is recommended for use in clinics, where DXA is the main body composition assessment technique.

It is increasingly recognised that the use of BMI cut-off points for diagnosing obesity (OB) and proxy measures for body fatness in a given population needs to take into account the potential impact of ethnicity on the BMI–fat % relationship in order to avoid adiposity status misclassification. This relationship was studied here in 377 Mauritian schoolchildren (200 boys and 177 girls, aged 7–13 years) belonging to the two main ethnic groups: Indian (South Asian descent) and Creole (African/Malagasy descent), with body composition assessed using an isotopic 2H dilution technique as reference. The results indicate that for the same BMI, Indians have more body fat (and less lean mass) than Creoles among both boys and girls: linear regression analysis revealed significantly higher body fat % by 4–5 units (P < 0·001) in Indians than in Creoles across a wide range of BMI (11·6–34·2 kg/m2) and body fat % (5–52 %). By applying Deurenberg’s Caucasian-based equation to predict body fat % from WHO-defined BMI thresholds for overweight (OW) and OB, and by recalculating the equivalent BMI values using a Mauritian-specific equation, it is shown that the WHO BMI cut-offs for OB and OW would need to be lowered by 4·6–5·9 units in Indian and 2·0–3·7 units in Creole children in the 7–13-year-old age group. These results have major implications for ethnic-based population research towards improving the early diagnosis of excess adiposity in this multi-ethnic population known to be at high risk for later development of type 2 diabetes and CVD.

Saliva and urine are the two main body fluids sampled when breast milk intake is measured with the 2H oxide dose-to-mother technique. However, these two body fluids may generate different estimates of breast milk intake due to differences in isotope enrichment. Therefore, we aimed to assess how the estimated amount of breast milk intake differs when based on saliva and urine samples and to explore whether the total energy expenditure of the mothers is related to breast milk output. We used a convenience sample of thirteen pairs of mothers and babies aged 2–4 months, who were exclusively breastfed and apparently healthy. To assess breast milk intake, we administered doubly labelled water to the mothers and collected saliva samples from them, while simultaneously collecting both saliva and urine from their babies over a 14-d period. Isotope ratio MS was used to analyse the samples for 2H and 18O enrichments. Mean breast milk intake based on saliva samples was significantly higher than that based on urine samples (854·5 v. 812·8 g/d, P = 0·029). This can be attributed to slightly higher isotope enrichments in saliva and to a poorer model fit for urine samples as indicated by a higher square root of the mean square error (14·6 v. 10·4 mg/kg, P = 0·001). Maternal energy expenditure was not correlated with breast milk output. Our study suggests that saliva sampling generates slightly higher estimates of breast milk intake and is more precise as compared with urine and that maternal energy expenditure does not influence breast milk output.

The study aimed at assessing stunting, wasting and breast-feeding as correlates of body composition in Cambodian children. As part of a nutrition trial (ISRCTN19918531), fat mass (FM) and fat-free mass (FFM) were measured using 2H dilution at 6 and 15 months of age. Of 419 infants enrolled, 98 % were breastfed, 15 % stunted and 4 % wasted at 6 months. At 15 months, 78 % were breastfed, 24 % stunted and 11 % wasted. Those not breastfed had lower FMI at 6 months but not at 15 months. Stunted children had lower FM at 6 months and lower FFM at 6 and 15 months compared with children with length-for-age z ≥0. Stunting was not associated with height-adjusted indexes fat mass index (FMI) or fat-free mass index (FFMI). Wasted children had lower FM, FFM, FMI and FFMI at 6 and 15 months compared with children with weight-for-length z (WLZ) ≥0. Generally, FFM and FFMI deficits increased with age, whereas FM and FMI deficits decreased, reflecting interactions between age and WLZ. For example, the FFM deficits were –0·99 (95 % CI –1·26, –0·72) kg at 6 months and –1·44 (95 % CI –1·69; –1·19) kg at 15 months (interaction, P<0·05), while the FMI deficits were –2·12 (95 % CI –2·53, –1·72) kg/m2 at 6 months and –1·32 (95 % CI –1·77, –0·87) kg/m2 at 15 months (interaction, P<0·05). This indicates that undernourished children preserve body fat at the detriment of fat-free tissue, which may have long-term consequences for health and working capacity.

Excess weight loss while minimising fat-free mass (FFM) loss is important for health. Travel is a particular period at risk for weight gain and for which the effects of a short-term intensive weight loss programme have not been studied. Therefore, we studied the effect of a novel, 1-week supervised health travel programme combining high volume, low-to-moderate intensity exercise and energy intake restriction on weight, body composition and health outcomes in adults. Weight was also monitored for 12 weeks after the programme. In all, thirty-six subjects (nineteen men, seventeen women) consisting of sixteen excess-weight (BMI: 27·1 (sd 1·7) kg/m2) and twenty healthy-weight (BMI: 22·3 (sd 1·8) kg/m2) individuals participated. Subjects performed 1 h of slow-paced intermittent jogging three times per d and other leisure activities, whereas consuming only provided foods without water restriction. Body mass significantly decreased from pre- to post-intervention in excess-weight and healthy-weight individuals (−3·5 (sd 1·5) and −3·5 (sd 1·3) %, respectively; P<0·001 for both), and losses were maintained at 12 weeks post-intervention in both groups (−6·3 (sd 3·8) and −1·7 (sd 4·0) %, respectively; P<0·01 for both). Fat mass also significantly decreased in both groups (excess weight: −9·2 (sd 4·6) %: healthy weight: −13·4 (sd 9·0) %; P<0·01 for both), whereas FFM was maintained. Similar improvements were observed for blood biochemistry and pressure in both groups. This short-term weight loss intervention yielded favourable outcomes in both excess- and healthy-weight adults, particularly a 3·5 % weight loss with no significant change to FFM. In addition, participants maintained weight loss for at least 12 weeks. Of multiple programme choices, the Health Tourism weight loss programme’s results indicate that it is a viable option.

Two, three and four compartment (2C, 3C and 4C) models of body composition are popular methods to measure fat mass (FM) and fat-free mass (FFM) in athletes. However, the impact of food and fluid intake on measurement error has not been established. The purpose of this study was to evaluate standardised (overnight fasted, rested and hydrated) v. non-standardised (afternoon and non-fasted) presentation on technical and biological error on surface anthropometry (SA), 2C, 3C and 4C models. In thirty-two athletic males, measures of SA, dual-energy X-ray absorptiometry (DXA), bioelectrical impedance spectroscopy (BIS) and air displacement plethysmography (BOD POD) were taken to establish 2C, 3C and 4C models. Tests were conducted after an overnight fast (duplicate), about 7 h later after ad libitum food and fluid intake, and repeated 24 h later before and after ingestion of a specified meal. Magnitudes of changes in the mean and typical errors of measurement were determined. Mean change scores for non-standardised presentation and post meal tests for FM were substantially large in BIS, SA, 3C and 4C models. For FFM, mean change scores for non-standardised conditions produced large changes for BIS, 3C and 4C models, small for DXA, trivial for BOD POD and SA. Models that included a total body water (TBW) value from BIS (3C and 4C) were more sensitive to TBW changes in non-standardised conditions than 2C models. Biological error is minimised in all models with standardised presentation but DXA and BOD POD are acceptable if acute food and fluid intake remains below 500 g.

The aims of this study were to develop and validate a prediction equation of fat-free mass (FFM) based on bioelectrical impedance analysis (BIA) and anthropometry using air-displacement plethysmography (ADP) as a reference in Asian neonates and to test the applicability of the prediction equations in an independent Western cohort. A total of 173 neonates at birth and 140 at two weeks of age were included. Multiple linear regression analysis was performed to develop the prediction equations in a two-third randomly selected subset and validated on the remaining one-third subset at each time point and in an independent Queensland cohort. FFM measured by ADP was the dependent variable, and anthropometric measures, sex and impedance quotient (L2/R50) were independent variables in the model. Accuracy of prediction equations was assessed using intra-class correlation and Bland–Altman analyses. L2/R50 was the significant predictor of FFM at week two but not at birth. Compared with the model using weight, sex and length, including L2/R50 slightly improved the prediction with a bias of 0·01 kg with 2 sd limits of agreement (LOA) (0·18, −0·20). Prediction explained 88·9 % of variation but not beyond that of anthropometry. Applying these equations to the Queensland cohort provided similar performance at the appropriate age. However, when the Queensland equations were applied to our cohort, the bias increased slightly but with similar LOA. BIA appears to have limited use in predicting FFM in the first few weeks of life compared with simple anthropometry in Asian populations. There is a need for population- and age-appropriate FFM prediction equations.

Equations for predicting body composition from bioelectrical impedance analysis (BIA) parameters are age-, sex- and population-specific. Currently there are no equations applicable to women of reproductive age in rural South Asia. Hence, we developed equations for estimating total body water (TBW), fat-free mass (FFM) and fat mass in rural Bangladeshi women using BIA, with 2H2O dilution as the criterion method. Women of reproductive age, participating in a community-based placebo-controlled trial of vitamin A or β-carotene supplementation, were enrolled at 19·7 (sd 9·3) weeks postpartum in a study to measure body composition by 2H2O dilution and impedance at 50 kHz using multi-frequency BIA (n 147), and resistance at 50 kHz using single-frequency BIA (n 82). TBW (kg) by 2H2O dilution was used to derive prediction equations for body composition from BIA measures. The prediction equation was applied to resistance measures obtained at 13 weeks postpartum in a larger population of postpartum women (n 1020). TBW, FFM and fat were 22·6 (sd 2·7), 30·9 (sd 3·7) and 10·2 (sd 3·8) kg by 2H2O dilution. Height2/impedance or height2/resistance and weight provided the best estimate of TBW, with adjusted R2 0·78 and 0·76, and with paired absolute differences in TBW of 0·02 (sd 1·33) and 0·00 (sd 1·28) kg, respectively, between BIA and 2H2O. In the larger sample, values for TBW, FFM and fat were 23·8, 32·5 and 10·3 kg, respectively. BIA can be an important tool for assessing body composition in women of reproductive age in rural South Asia where poor maternal nutrition is common.

The present study was conducted to evaluate and compare the physiological responses of sheep and goats to water restriction using the deuterium dilution technique (D2O) to predict the total water intake (TWI) in both species. In two consecutive trials, 10 non-lactating Boer goats and 10 non-lactating German black-head mutton ewes were each randomly allocated into a treatment and a control group. In the control groups (n = 5, for each species), water was offered ad libitum, whereas the treatment groups (n = 5, for each species) received water 3 h/day on experimental days 8 to 14 and 6 h every 2 days on experimental days 15 to 22. The respiratory rate, rectal temperature, body mass and drinking behaviour were also recorded. The TWI was estimated by D2O for each animal. Water restriction for 21 h/day or 42 h/2 days had no significant (P > 0.05) effect on water intake (WI), feed intake, WI to dry matter intake ratio or body mass in both species. The absence of differences between species in their WIs was also confirmed using D2O. However, sheep had higher respiratory rates and rectal temperatures than goats in both control and treatment groups. Both species showed the ability to tolerate a moderate water shortage by activating several physiological mechanisms and behavioural strategies.

The aim of this study was to test whether the deuterium oxide dilution technique accurately predicts water intake in sheep and goats. Two other issues were also studied: (i) a comparison of water intake in sheep and goats and (ii) an assessment of whether observations of drinking behaviour can accurately measure the water intake. In this study, eight dry Boer goats and eight dry German Black Head Mutton ewes were kept under controlled stable conditions. Animals had access to hay and water ad libitum. Diurnal drinking behaviour was recorded by video. Individual daily water intake was measured and estimated for 2 weeks by re-weighing water buckets and from water kinetics using the deuterium oxide dilution technique, respectively. In addition, dry matter intakes were directly measured and were significantly higher in sheep than in goats. The average daily water consumption by drinking differed significantly between the two species, with higher intakes in sheep than in goats. Total body water expressed as a percentage of body mass did not differ between species. Measurement methods of total water intake (TWI) using deuterium oxide dilution and re-weighing water buckets did not differ significantly in both species (P = 0.926). Results obtained for measured and estimated TWI confirm that the isotope dilution technique gives reliable results for estimates of water intake in sheep and goats. The higher amount of water intake in sheep was also reflected by their drinking behaviour. Sheep spent approximately 0.3% per 24-h drinking, while Boer goats spent only 0.1%. However, measured and estimated TWIs were only moderately correlated to the daily time spent drinking. The lower water intake found in Boer goats confirms a superior water management capacity compared with Black Head Mutton sheep even under temperate conditions.

The association of early postnatal growth with diseases in adults such as hypertension, type 2 diabetes and CHD has generated interest in studying postnatal growth. Bioelectrical impedance analysis (BIA) is a useful measure to estimate total body water (TBW) and fat-free mass (FFM). We evaluated three published equations (Fjeld et al. (Pediatr Res (1990) 27, 98–102), Bocage (MSc Thesis (1988) University of West Indies) and Kushner et al. (Am J Clin Nutr (1992) 56, 835–839) to measure TBW and derived FFM based on BIA, using 2H2O dilution as a reference method for suitability in infants in India. In a cross-sectional study in seventy-eight apparently healthy infants aged 6–24 months from the urban poor attending an immunisation clinic at a hospital in Kolkata, we measured their length to the nearest 0·1 cm, weight to the nearest 10 g, resistance at 50 kHz using BIA and TBW using 2H2O dilution. TBW was derived using three published BIA-based equations and compared with TBW using 2H2O dilution. Based on the BIA equations of Fjeld et al., Bocage and Kushner et al., the mean TBW values were 2·46 % (P < 0·001), 4·62 % (P < 0·001) and 9·50 % (P < 0·001) lower than the reference 2H2O method, respectively. All three published BIA-based equations consistently underestimated the TBW and FFM and appeared inadequate for studying infants in India. The equation described by Fjeld et al. gave the smallest deviation from the reference method and may be used for field studies. New equations based on population-specific data are desirable for a more precise measure of TBW.

Rapid postnatal growth in low-birth weight infants increases the risk of hypertension, CHD and type 2 diabetes in adult life. To provide validated tools to study the growth in South Asian infants, we evaluated two published equations to measure total body water (TBW) and fat-free mass (FFM) based on anthropometry in 6- to 24-month-old infants, using 2H2O dilution. In a method-comparison study in seventy-eight infants aged 6–24 months (forty-two girls and thirty-six boys) from the urban poor attending an immunisation clinic of a hospital in Kolkata, we measured their length to the nearest 0·1 cm, weight to the nearest 10 g and TBW using 2H2O dilution. The calculated TBW in kg (TBWkg) and FFM in kg (FFMkg) using two equations based on the length and weight were each compared with TBWkg and FFMkg calculated from 2H2O dilution. The mean FFMkg were 7·31 (sd 1·11), 7·13 (sd 1·08) and 7·26 (sd 1·13) by the 2H2O dilution method, and the anthropometry equations of Mellits and Cheek (AN-1) and Morgenstern et al. (AN-2), respectively. The mean of the paired difference in FFMkg was 0·18 (sem 0·06) and 0·04 (sem 0·07) between 2H2O, and AN-1 and AN-2, respectively. There is a good agreement for FFM derived by AN-2 with 2H2O dilution. The former is 1 % lower than that obtained from the reference method (P = 0·28). The AN-2 equation is useful for evaluating FFM in infants in India.